I. Field
The following description relates generally to wireless communications, and more particularly to forming and sending a partial status report that will fit in an uplink grant or downlink assignment.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple access terminals. Each access terminal can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to access terminals, and the reverse link (or uplink) refers to the communication link from access terminals to base stations. This communication link can be established via a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
MIMO systems commonly employ multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas can be decomposed into NS independent channels, which can be referred to as spatial channels, where NS≦{NT, NR}. Each of the NS independent channels corresponds to a dimension. Moreover, MIMO systems can provide improved performance (e.g., increased spectral efficiency, higher throughput and/or greater reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized.
MIMO systems can support various duplexing techniques to divide forward and reverse link communications over a common physical medium. For instance, frequency division duplex (FDD) systems can utilize disparate frequency regions for forward and reverse link communications. Further, in time division duplex (TDD) systems, forward and reverse link communications can employ a common frequency region so that the reciprocity principle allows estimation of the forward link channel from reverse link channel.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to an access terminal. An access terminal within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, an access terminal can transmit data to the base station or another access terminal.
The Radio Link Control (RLC) protocol is typically responsible for segmentation of (header-compressed) Internet Protocol (IP) packets from the Packet Data Convergence Protocol (PDCP) into smaller units, Radio Link Control (RLC) Protocol Data Units (PDUs). Moreover the RLC protocol is also tasked with retransmission of erroneously received PDUs, as well as duplicate removal and concatenation of received PDUs. Additionally, the RLC ensures in-sequence delivery of RLC Service Data Units (SDUs) to upper layers.
The RLC retransmission mechanism can be responsible from providing error-free delivery of data to higher layers. This can be accomplished by a transmission protocol that operates between the RLC entities in the receiver and the transmitter. By monitoring the sequence numbers, the receiving RLC can identify missing PDUs. Status reports can then be fed back to the transmitting RLC, requesting retransmission of missing PDUs. When to feedback a status report can be configurable, but a report typically contains information about multiple PDUs and is generally transmitted relative infrequently. Based at least in part on the received status report, the RLC entity at the transmitter can take appropriate action and retransmit the missing PDUs if required.
When the RLC is configured to request retransmission of missing PDUs, it is said to be operating in Acknowledge Mode (AM) which is typically employed for Transmission Control Protocol (TCP) based services such as file transfer where error free data delivery is necessary.
The RLC can also be configured in Unacknowledged Mode (UM) and Transparent Mode (TM). In UM, in-sequence delivery to higher layers can be provided, but no retransmissions of missing PDUs are requested. Generally, UM is utilized for services such as Voice over Internet Protocol (VoIP) services where error free delivery is less of a concern compared to short delivery time. TM, although supported, is only used for specific purposes such as random access.